1 files changed, 69 insertions, 7 deletions

diff --git a/documentation/ref-manual/ref-variables.rst b/documentation/ref-manual/ref-variables.rst
index a8375cd37c..227c81fc39 100644
--- a/documentation/ref-manual/ref-variables.rst
+++ b/documentation/ref-manual/ref-variables.rst
@@ -3337,9 +3337,18 @@ system and gives an overview of their function and contents.
    :term:`INCOMPATIBLE_LICENSE`
       Specifies a space-separated list of license names (as they would
       appear in :term:`LICENSE`) that should be excluded
-      from the build. Recipes that provide no alternatives to listed
+      from the build (if set globally), or from an image (if set locally
+      in an image recipe).
+
+      When the variable is set globally, recipes that provide no alternatives to listed
       incompatible licenses are not built. Packages that are individually
       licensed with the specified incompatible licenses will be deleted.
+      Most of the time this does not allow a feasible build (because it becomes impossible
+      to satisfy build time dependencies), so the recommended way to
+      implement license restrictions is to set the variable in specific
+      image recipes where the restrictions must apply. That way there
+      are no build time restrictions, but the license check is still
+      performed when the image's filesystem is assembled from packages.
 
       .. note::
 
@@ -3811,6 +3820,15 @@ system and gives an overview of their function and contents.
 
          KERNEL_ARTIFACT_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}"
 
+   :term:`KERNEL_DTC_FLAGS`
+      Specifies the ``dtc`` flags that are passed to the Linux kernel build
+      system when generating the device trees (via ``DTC_FLAGS`` environment
+      variable).
+
+      In order to use this variable, the
+      :ref:`kernel-devicetree <ref-classes-kernel-devicetree>` class must
+      be inherited.
+
    :term:`KERNEL_EXTRA_ARGS`
       Specifies additional ``make`` command-line arguments the OpenEmbedded
       build system passes on when compiling the kernel.
@@ -3837,10 +3855,10 @@ system and gives an overview of their function and contents.
       ::
 
          KERNEL_EXTRA_FEATURES ?= "features/netfilter/netfilter.scc features/taskstats/taskstats.scc"
-         KERNEL_FEATURES_append = "${KERNEL_EXTRA_FEATURES}"
-         KERNEL_FEATURES_append_qemuall = "cfg/virtio.scc"
+         KERNEL_FEATURES_append = " ${KERNEL_EXTRA_FEATURES}"
+         KERNEL_FEATURES_append_qemuall = " cfg/virtio.scc"
          KERNEL_FEATURES_append_qemux86 = " cfg/sound.scc cfg/paravirt_kvm.scc"
-         KERNEL_FEATURES_append_qemux86-64 = "cfg/sound.scc"
+         KERNEL_FEATURES_append_qemux86-64 = " cfg/sound.scc"
 
    :term:`KERNEL_FIT_LINK_NAME`
       The link name of the kernel flattened image tree (FIT) image. This
@@ -4039,7 +4057,7 @@ system and gives an overview of their function and contents.
          SRCREV_machine_core2-32-intel-common = "43b9eced9ba8a57add36af07736344dcc383f711"
          KMACHINE_core2-32-intel-common = "intel-core2-32"
          KBRANCH_core2-32-intel-common = "standard/base"
-         KERNEL_FEATURES_append_core2-32-intel-common = "${KERNEL_FEATURES_INTEL_COMMON}"
+         KERNEL_FEATURES_append_core2-32-intel-common = " ${KERNEL_FEATURES_INTEL_COMMON}"
 
       The ``KMACHINE`` statement says
       that the kernel understands the machine name as "intel-core2-32".
@@ -7138,6 +7156,32 @@ system and gives an overview of their function and contents.
    :term:`SSTATE_DIR`
       The directory for the shared state cache.
 
+   :term:`SSTATE_EXCLUDEDEPS_SYSROOT`
+      This variable allows to specify indirect dependencies to exclude
+      from sysroots, for example to avoid the situations when a dependency on
+      any ``-native`` recipe will pull in all dependencies of that recipe
+      in the recipe sysroot. This behaviour might not always be wanted,
+      for example when that ``-native`` recipe depends on build tools
+      that are not relevant for the current recipe.
+
+      This way, irrelevant dependencies are ignored, which could have
+      prevented the reuse of prebuilt artifacts stored in the Shared
+      State Cache.
+
+      :term:`SSTATE_EXCLUDEDEPS_SYSROOT` is evaluated as two regular
+      expressions of recipe and dependency to ignore. An example
+      is the rule in :oe_git:`meta/conf/layer.conf </openembedded-core/tree/meta/conf/layer.conf>`::
+
+         # Nothing needs to depend on libc-initial
+         # base-passwd/shadow-sysroot don't need their dependencies
+         SSTATE_EXCLUDEDEPS_SYSROOT += "\
+             .*->.*-initial.* \
+             .*(base-passwd|shadow-sysroot)->.* \
+         "
+
+      The ``->`` substring represents the dependency between
+      the two regular expressions.
+
    :term:`SSTATE_MIRROR_ALLOW_NETWORK`
       If set to "1", allows fetches from mirrors that are specified in
       :term:`SSTATE_MIRRORS` to work even when
@@ -7533,7 +7577,7 @@ system and gives an overview of their function and contents.
       ``SYSTEMD_BOOT_CFG`` as follows:
       ::
 
-         SYSTEMD_BOOT_CFG ?= "${:term:`S`}/loader.conf"
+         SYSTEMD_BOOT_CFG ?= "${S}/loader.conf"
 
       For information on Systemd-boot, see the `Systemd-boot
       documentation <http://www.freedesktop.org/wiki/Software/systemd/systemd-boot/>`__.
@@ -8736,4 +8780,22 @@ system and gives an overview of their function and contents.
 
       The default value of ``XSERVER``, if not specified in the machine
       configuration, is "xserver-xorg xf86-video-fbdev xf86-input-evdev".
-   
+
+   :term:`XZ_THREADS`
+      Specifies the number of parallel threads that should be used when
+      using xz compression.
+
+      By default this scales with core count, but is never set less than 2
+      to ensure that multi-threaded mode is always used so that the output
+      file contents are deterministic. Builds will work with a value of 1
+      but the output will differ compared to the output from the compression
+      generated when more than one thread is used.
+
+      On systems where many tasks run in parallel, setting a limit to this
+      can be helpful in controlling system resource usage.
+
+    :term:`XZ_MEMLIMIT`
+      Specifies the maximum memory the xz compression should use as a percentage
+      of system memory. If unconstrained the xz compressor can use large amounts of
+      memory and become problematic with parallelism elsewhere in the build.
+      "50%" has been found to be a good value.